Screw drive

ABSTRACT

The specification discloses the combination of a threaded member and a nut arrangement moveable therealong in which the nut arrangement comprises a frame moveable relative to the member parallel to the axis thereof and having at least one ring rotatably mounted therein and engaging a circumferential region of the thread on said member whereby the area of interengagement of the ring and the thread is sickle shaped. The ring is inclined to be disposed in the plane of the region of the thread engaged thereby. Advantageously, more than one ring is employed with the rings spaced axially and each engaging the thread in a different circumferential region.

United States Patent Gartner SCREW DRIVE [72] lnventor: Robert Gartner, Freiherr v. Stein Strasse 8, 6308 Butzbach, Hessen, Germany [22] Filed: May 27,1971

[21] Appl. No.: 147,470

[30] Foreign Application Priority Data May 30, 1970 Germany ..P 20 26 550.3

[52] US. Cl. ..74/424.8, 74/89.l5 R [51] Int. Cl. ..Fl6h 1/18, F16h 27/02 [58] Field of Search ,...74/424.8 R, 89.15 R, 25, 459, 74/464, 465

[56] References Cited UNITED STATES PATENTS 3,003,362 10/1961 Martens ..74/424.8 R

[451 Oct. 17, 1972 3,003,361 10/1961 Boutwell ..74/424.8R

Primary Examiner-Carlton R. Croyle Assistant Examiner-Frank McKenzie, Jr. Attorney-Walter Becker [57] ABSTRACT The specification discloses the combination of a threaded member and a nut arrangement moveable therealong in which the nut arrangement comprises a frame moveable relative to the member parallel to the axis thereof and having at least one ring rotatably mounted therein and engaging a circumferential region of the thread on said member whereby the area of interengagement of the ring and the thread is sickle shaped. The ring is inclined to be disposed in the plane of the region of the thread engaged thereby. Advantageously, more than one ring is employed with the rings spaced axially and each engaging the thread in a different circumferential region.

16 Claims, 20 Drawing Figures PATENTEDum 17 m2 SHEET 1 [IF 4 INVENTOR. z; Z917 PATENTEDnm 11 m2 SHEET 2 OF 4 INVENTOR. Z pin/53); BY

PATENTEDnm 17 I972 3,698,258

sum 3 [1F 4 INVENTOR. 7%:9/ 43%,

SCREW DRIVE The presentinvention relates to a screw drive with a threaded spindle and transmitting meanscooperating therewith.

With screw drives of the above mentioned type it is known to provide a roller body between the flanks of the spindle thread and a nut. The degree of efficiency of such designs is considerably affected by damming up of the roller bodies.

With other heretofore known designs of screw drives, satellite spindles are provided between the threaded spindle and the nut. With designs of this type, the degree of efficiency is decreased by friction losses which are caused by a multiple deviation of the power path.

Furthermore, screw drives have become known, according to which, conical rollers engage the threads of the spindle. In view of the line contact between the conical rollers and the threads, disadvantageous high surface pressures are exerted under unfavorable power transmission conditions. The short roller diameters of the conical rollers furthermore bring about an undesired high speed.

It is an object of the present invention to provide a screw drive which will overcome the above mentioned drawbacks and which will eliminate the high surface pressure exerted upon the above mentioned heretofore known screw drives.

These and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawings, in which:

FIG. 1 illustrates a top view of a screw drive according to the present invention.

FIG. 2 is an end view of FIG. 1 as seen in the direction of the arrow A.

FIG. 3 shows a detail of the system shown in FIGS. 1 and 2.

FIG. 4 is a top view of a modified screw drive according to the invention.

FIG. 5 is an end view of FIG. 4 as seen in the direction of the arrow C of FIG. 4.

FIG. 6 is a view similar to that of FIG. 4 as seen in the direction of the arrow B.

FIG. 7 shows a detail of the arrangement of FIGS. 4-6.

FIGS. 8-20 illustrate details of modifications according to the present invention.

The screw drive according to the present invention with a threaded spindle and a transmission member cooperating therewith is characterized primarily in that the transmission member arranged on a frame or housing guided by the spindle itself or outside the same is designed as a ring adapted to roll relative to the frame or housing in a sliding-free manner, said ring partially directly engaging the thread of the screw spindle and being inclined in the direction of the pitch of the spindle while being arranged in the frame or housing.

The rolling ring or collar forms a sickle-shaped support or pressure surface with the thread of the spindle.

According to one of the embodiments of the screw drive according to the invention, the roller ring may be connected with the inner ring of an antifriction bearing which has its outer race ring connected to the frame or housing. The collar is furthermore eccentrically arranged with regard to the longitudinal axis of the spindle.

2 According to a further development of the invention, the collar has a larger inner diameter than the outer diameter of the spindle. The collarmay, however, also rest on vertically arranged rollers or self-aligning ball bearings arranged on the frame or housing and the threaded ring may be connected with the axis of the roller or ball bearings and the roller or bearings may roll directly on the frame.

Referring now to the drawings in detail and, more specifically, to the embodiments of FIGS. 1 to 3, the arrangement shown therein comprises a threaded spindle l with the longitudinal axis 2 (F I68. 2 and 3). The spindle 3 is surrounded by three antifriction bearings 3, 4 and 5, of different sizes, which are inclined relative to the horizontal as shown in FIG. 1. This inclination corresponds to the position of the thread 1a of spindle l.

The outer ring 6 of each antifriction bearing 3, 4, 5 is by means of jaws or clamping members 7 held in its position on three threaded spindles 8. The jaws or clamping members 7 may be adjusted on the fine thread of the threaded spindles 8 and preferably have a certain flexibility or are provided with bent portions 7a. The clamping members may be elastic but, if desired, may also be provided with similar bent portions.

Connected to the inner race ring 9 of each antifriction bearing 3, 4, 5, which ring in a contact-free manner surrounds the spindle 1 while taking into consideration the inclination of the antifriction bearing, is a disc-shaped collar 3a, 4a, 5a. This connection may be effected, for instance, by screwing or welding, and the collar 3a, 4a, 5a, engages a thread winding of the thread 1a of spindle 1. The inner diameter of said thread winding is greater than the spindle diameter and has a sickle-shaped support on one of the thread windings. This sickle-shaped supporting zone 4b can be seen in FIG. 2 at the edge of the inner ring 4a of antifriction bearing 4 and is indicated by shading.

Shown in FIGS. 2 and 3 are center points 3d, 4d, 5d, of the collars 3a, 4aand 5a, of the antifriction bearings 3, 4 and 5, which latter are located outside the spindle axis 2 in conformity with the size of the collar.

The line of steepest gradient 3c, 40, 5c, of the embodiments according to FIGS. 1 to 3 are offset with regard to each other by an angle of The threaded spindles 8 are in a manner not illustrated, but in a manner known per se, held in a lower plate 11 and an upper plate 12. The upper plate 12 has rollers 13 which are inclined by an angle equalling the pitch angle. These rollers 13 will assure the radial guiding of the frame formed by the bars and plates and thereby also the guiding of the antifriction bearings. In conformity with the respective type of load these rollers may be of different size and may be described at will. The lower plate 11 is provided with a bushing 14 which guides the plate 1 l radially.

In conformity with the different sizes of the collar 3, 4, 5 engaging the thread, the sickle-shaped support of this collar on the corresponding thread winding la of spindle 1 will vary.

The offset angle of the individual collars 3, 4, 5 and the number of the same may be selected at will in conformity with the load.

According to the embodiment of FIGS. 4 to 7, the threaded spindle is again designated with the reference numeral 1 and the collar which engages the thread 1 of the spindle is designated with the reference numeral 16. As will be evident from FIGS. 5 and 6, the longitudinal central line of the disc-shaped ring 16 is located laterally adjacent to the longitudinal central line 18 of spindle 1. Ring 16 has similar to the rings 30, 4a, 5a of FIGS 1-3 an inclination which corresponds to the pitch of the threaded spindle l. The inner marginal area 19 of ring 16 extends close to the bottom of the thread la of the threaded spindle 1 (FIG. 5). It may contact the bottom of the thread when the ring 16 takes over a radial guiding function.

The force K acts in a downward direction upon the threaded spindle 1. The contact and power transmission zone 20 between the ring 16 and the threaded spindle l is also in FIG. 5 of a sickle-shape and is shown by shading. The pressure center 21 is located symmetrically within the sickle-shaped contact and power transmission zone 20.

The support of ring 16 is in conformity with the embodiments of FIGS. 4-7 effected on both sides of the spindle l by aligning ball bearings 22,23 of different sizes which may be provided with sleeves which are able to adapt themselves to the deformation of the ring 16 under load. Instead of self-aligning ball bearings, also roller bearings with cardanic suspension may be employed.

The bearing axes 22a, 23a, of the self-aligning ball bearings 22, 23 are connected to the supports 24 which in their turn are connected to a bushing 25. In conformity with the position of ring 16, the spacing of the bearings 22, 23 from the spindle axis 18 varies.

The points of engagement 26, 27 or lines of the ball bearings 22, 23 with the ring 16 are located on a straight line on which also the pressure center 21 is at least approximately located.

As will furthermore be seen from FIG. 5, the larger one of the two bearings or rollers 22, 23 carries the main load, said larger roller 22 being adjacent to the pressure center 21.

The bushing 25 rests against a fixed frame or the machine part M. If, during a rotation of the spindle, the force K acts in the longitudinal direction of the spindle, said force K is first transmitted to the ring 16 which rotates in view of the slight friction in the sickle-shaped supporting zone 20, and by the said ring 16 is transmitted to the rollers 22, 23 which may also be directly journalled in a fixed framework. The ring 16 may adapt itself to the disuniformities of the thread 121 of spindle 1 and can adjust itself while freely tilting about the straight line (FIG. 5) passing through the points 21, 26 and 27. This is advantageous for an easy movement and for the stresses to which the parts are subjected. On the other hand, ring 16 is able easily to adapt itself to the pitch 1a of the thread of the spindle.

The radial guiding of ring 16 is taken over by the rollers 28 which are connected either to one support 24 or the fixed frame or machine part M.

FIG. 7 shows an arrangement according to which the ring 16 rolls on crowned rollers 30, 31, which correspond to the ball bearings 22, 23 of FIGS. 4-6. One of the two rollers may have a bead 29, flange, or the like, whereby ring 16 will be guided radially. Ring 16 may, in its turn, also have a concave or convex annular bottom surface.

FIG. 8 shows a ring 30 according to which for purposes of a radial guiding, inclined slots 31 will yield a more favorable supporting zone, a good adaptation, slight friction and very satisfactory lubricating possibilities. FIG. 9 shows an angled-off ring member 30a in which supporting members 32 defined by suitable arcs extend into the spindle thread. These supporting members 32 may also be designed in the form of pinions or studs.

For purposes of realizing the above outlined effects, also offset bores, milled portions, grooves, or the like, extending all the way or arranged only unilaterally may be employed.

In conformity with FIG. 10, the ring 33 extends in the manner of pliers around the winding 34 of the threaded spindle 1. Inasmuch as a contact occurs on the threaded head, a radial guiding is here obtained. FIG. 11, however, shows the play on the threaded head and threaded bottom.

Referring now to FIG. 12, the rings 35, and the contracted pins 37, 38 may be adapted to set themselves in the manner of a cardanic joint. In view of the constriction of said pins, an elastic length combination will be obtained. The two roller rings 35, 36 are combined with a sleeve 39 which rolls on roller pairs 40,41. If desired, also a plurality of rings may be arranged in a sleeve, which rings roll on a plurality of roller paths. The rollers may also have their axis journalled on the sleeve.

FIG. 13 diagrammatically illustrates a separation of the roller ring in a part 42 which meshes with the spindle thread la, and a second part 43 which rests on rollers 44 or itself carries the rollers. For elastic adaptation, the spring elements 45, 46 are provided as connection between the two ring members 42 and 43.

According to the embodiment of FIG. 14 the roller ring 47 moves in guiding means 48 while lubricating oil, for instance, in the direction of the indicated arrows is added. The arrangement may also form a hydrodynamic or hydrostatic lubrication. FIG. 15 illustrates how two outwardly rolling inclined rollers 49 are, by bearings 50, firmly connected to the ring 51.

FIG. 16 illustrates how a ring 52 is arranged in the interior of a hollow spindle 53. FIG. 17 represents a double acting unit comprising two rings 54 and 55, according to which the rollers 56, 57 and 58, 59 are braced against each other in the direction of the arrows W so that absolute freedom of play will be assured.

FIG. 18 furnishes the same effect as the rollers 60, 61; 62,63 but are arranged adjacent to each other. In FIG. 19 the ring 64 is pressed in radial direction into the thread la of spindle 1. Finally, FIG. 20 represents a further possibility of arranging supporting rollers 65, 66 on ring 64. The connecting line between the axes of rotation 65a, 66a, of the supporting rollers will also in this instance pass through the pressure center 67 of the sickle-shaped load zone 68 indicated by shading.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings, but also comprises any modifications within the scope of the appended claims.

What is claimed is:

1. In combination: a member having a screw thread and a frame guided for relative movement parallel to the axis of the screw thread, ring means on the frame engaging said screw thread in a predetermined circumferential fractional region thereof and inclined to the axis of said screw thread in the plane of said region thereof, and means rollingly supporting said ring means on said frame in said plane, said member and frame being adapted for relative rotation on the said axis of said screw thread to cause relative axial movement between said member and said frame.

2. The combination according to claim 1 in which said screw thread is on the external surface of said member, said frame surrounding said member, and said ring means being larger in diameter than said member and also surrounding said member.

3. The combination according to claim 1 in which said ring means is supported on said frame eccentrically relative to the axis of said screw thread.

4. The combination according to claim 1 in which the area of engagement between said ring means and said screw thread is sickle shaped.

5. The combination according to claim 1 which includes an antifriction bearing interposed between said ring means and said frame.

6. The combination according to claim 1 in which said frame surrounds said member and is radially guided thereon, an antifriction bearing surrounding said member and having the outer race fixed to said frame, said ring means being fixed to the inner race of said bearing, and said ring means and bearing being eccentric to said member.

7. The combination according to claim 1 in which said ring means comprise a plurality of rings arranged in spaced relation along the axis of said screw thread and each engaging said screw thread in a respective circumferential region, said regions being spaced circumferentially about said member and each ring being disposed in the plane of the respective region of the screw thread engaged thereby.

8. The combination according to claim 1 which includes antifriction bearing means on said frame having outer races engaging said ring means at circumferentially spaced points, the said bearing means having the greatest load thereon being larger than the others thereof.

9. The combination according to claim 1 which includes antifriction bearings on said frame having axes generally radial to said ring means, said bearings having inner races connected to said frame and having outer races on which said ring means rests.

10. The combination according to claim 9 in which said bearings are so located in said frame relative to said ring means that a line joining the points of engagement of said bearings with said ring means passes substantially through the center of pressure of the region of interengagement of said ring means with said screw thread.

11. The combination according; to claim 1 which includes bearings in said frame engaging said ring means in the radial direction and preventing lateral movement thereof relative to said member.

12. The combination according to claim 1 in which said means rollingly supporting said ring means in said frame comprises antifriction bearings formed in part by one axial face of said ring means, said axial face being crowned.

13. The combination according to claim 1 which includes a ring element concentric with said ring means and axially spaced therefrom, said ring element being guided radially and connected to said ring means.

14. The combination according to claim 1 in which said ring means comprises a pair of rings axially spaced from each other, and means engaging said rings for transmitting axial thrusts therebetween.

15. The combination according to claim 1 which includes bearing means connected to said ring means, said bearing means rollingly engaging said frame.

16. The combination according to claim 7 in which each ring is guided in said frame so as to be non-radially moveable therein, said means rollingly supporting said rings in said frame comprising antifriction bearing means interposed between said rings and said frame and supporting each ring at the respective degree of inclination thereof to the axis of said screw thread, said rings being supported in said frame against bodily movement circumferentially of said frame. 

1. In combination: a member having a screw thread and a frame guided for relative movement parallel to the axis of the screw thread, ring means on the frame engaging said screw thread in a predetermined circumferential fractional region thereof and inclined to the axis of said screw thread in the plane of said region thereof, and means rollingly supporting said ring means on said frame in said plane, said member and frame being adapted for relative rotation on the said axis of said screw thread to cause relative axial movement between said member and said frame.
 2. The combination according to claim 1 in which said screw thread is on the external surface of said member, said frame surrounding said member, and said ring means being larger in diameter than said member and also surrounding said member.
 3. The combination according to claim 1 in which said ring means is supported on said frame eccentrically relative to the axis of said screw thread.
 4. The combination according to claim 1 in which the area of engagement between said ring means and said screw thread is sickle shaped.
 5. The combination according to claim 1 which includes an antifriction bearing interposed between said ring means and said frame.
 6. The combination according to claim 1 in which said frame surrounds said member and is radially guided thereon, an antifriction bearing surrounding said member and having the outer race fixed to said frame, said ring means being fixed to the inner race of said bearing, and said ring means and bearing being eccentric to said member.
 7. The combination according to claim 1 in which said ring means comprise a plurality of rings arranged iN spaced relation along the axis of said screw thread and each engaging said screw thread in a respective circumferential region, said regions being spaced circumferentially about said member and each ring being disposed in the plane of the respective region of the screw thread engaged thereby.
 8. The combination according to claim 1 which includes antifriction bearing means on said frame having outer races engaging said ring means at circumferentially spaced points, the said bearing means having the greatest load thereon being larger than the others thereof.
 9. The combination according to claim 1 which includes antifriction bearings on said frame having axes generally radial to said ring means, said bearings having inner races connected to said frame and having outer races on which said ring means rests.
 10. The combination according to claim 9 in which said bearings are so located in said frame relative to said ring means that a line joining the points of engagement of said bearings with said ring means passes substantially through the center of pressure of the region of interengagement of said ring means with said screw thread.
 11. The combination according to claim 1 which includes bearings in said frame engaging said ring means in the radial direction and preventing lateral movement thereof relative to said member.
 12. The combination according to claim 1 in which said means rollingly supporting said ring means in said frame comprises antifriction bearings formed in part by one axial face of said ring means, said axial face being crowned.
 13. The combination according to claim 1 which includes a ring element concentric with said ring means and axially spaced therefrom, said ring element being guided radially and connected to said ring means.
 14. The combination according to claim 1 in which said ring means comprises a pair of rings axially spaced from each other, and means engaging said rings for transmitting axial thrusts therebetween.
 15. The combination according to claim 1 which includes bearing means connected to said ring means, said bearing means rollingly engaging said frame.
 16. The combination according to claim 7 in which each ring is guided in said frame so as to be non-radially moveable therein, said means rollingly supporting said rings in said frame comprising antifriction bearing means interposed between said rings and said frame and supporting each ring at the respective degree of inclination thereof to the axis of said screw thread, said rings being supported in said frame against bodily movement circumferentially of said frame. 